Duplex - Cisco Catalyst 3750 Metro Command Reference Manual

duplex

duplex
Use the duplex interface configuration command to specify the duplex mode of operation for Fast
Ethernet and Gigabit Ethernet ports. Use the no form of this command to return the port to its default
value.
Syntax Description
auto
full
half
Defaults The default is auto for Fast Ethernet ports and for 1000BASE-T small form-factor pluggable (SFP)
modules.
The default is full for 100BASE-FX MMF SFP modules.
Command Modes Interface configuration
Command History Release
12.1(14)AX
12.2(25)EY
Usage Guidelines For Fast Ethernet ports, setting the port to auto has the same effect as specifying half if the attached
device does not autonegotiate the duplex parameter.
For Gigabit Ethernet ports, setting the port to auto has the same effect as specifying full if the attached
device does not autonegotiate the duplex parameter.
Certain ports can be configured to be either full duplex or half duplex. Applicability of this command
depends on the device to which the switch is attached.
If both ends of the line support autonegotiation, we highly recommend using the default autonegotiation
settings. If one interface supports autonegotiation and the other end does not, configure duplex and speed
on both interfaces; do use the auto setting on the supported side.
If the speed is set to auto, the switch negotiates with the device at the other end of the link for the speed
setting and then forces the speed setting to the negotiated value. The duplex setting remains as
configured on each end of the link, which could result in a duplex setting mismatch.
For 10/100 Mbps ports, if both speed and duplex are set to specific values, the link operates at the
negotiated speed and duplex value.
For 10/100/1000 Mbps ports, if both the speed and duplex are set to specific values, autonegotiation is
disabled.
Catalyst 3750 Metro Switch Command Reference
2-100
duplex {auto | full | half}
no duplex
Enable automatic duplex configuration; port automatically detects whether it
should run in full- or half-duplex mode, depending on the attached device mode.
Enable full-duplex mode.
Enable half-duplex mode (for Fast Ethernet ports only).
Modification
This command was introduced.
Support for the half keyword was added for the 100BASE-FX SFP module.
Chapter 2 Catalyst 3750 Metro Switch Cisco IOS Commands
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